title: Spectroscopic Raman study of sulphate precipitation sequence in Rio Tinto mining district (SW Spain).
abstract: Acidic waters and sulphate-rich precipitates are typical by-products of mining activity such as in Rio Tinto (Huelva, SW Spain). This river drains pyrite mines situated in the Iberian Pyrite Belt which have been in operation since the Bronze Age and probably constitutes the oldest continuously operating mining activity over the world. In the present work, we have used Raman spectroscopy to study a wide range of natural mineral samples collected at Rio Tinto which origin is related to evaporation and mineral transformation processes in a wet and extreme acidic environment. In addition, we simulated the phenomenon of mineral precipitation in controlled conditions by using a simulator developed at the laboratory evaporating natural water collected at Rio Tinto. Also, a series of experiments using the same waters as small droplets have been carried out using micro-Raman technique. The droplets were placed on substrates with different chemical composition and reactivity. The results reveal that the precipitation sequence occurred in Rio Tinto mainly comprises copiapite and coquimbite group minerals followed by several other low hydrated iron sulphates. The experiments carried out on droplets allow estimating with higher accuracy the precipitation sequence.
authors.affiliation: Unidad Asociada UVA-CSIC al Centro de Astrobiología, Valladolid, Spain, rull@fmc.uva.es.
authors.forename: Fernando
authors.initials: F
authors.lastname: Rull
authors.forename: Julia
authors.initials: J
authors.lastname: Guerrero
authors.forename: Gloria
authors.initials: G
authors.lastname: Venegas
authors.forename: Fernando
authors.initials: F
authors.lastname: Gázquez
authors.forename: Jesús
authors.initials: J
authors.lastname: Medina
mesh_terms: D011232:Chemical Precipitation; D003890:Desiccation; D008906:Mining; D045483:Rivers / Q000737:chemistry*; D013030:Spain; D013059:Spectrum Analysis, Raman; D013431:Sulfates / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D013431:Sulfates; D014874:Water Pollutants, Chemical